Air brake system



Sept. 28, 1937. CASTRO 2,094,205

AIR BRAKE SYSTEM Filed Oct. 28. 1935 INVENTORi LIZANDRO FERNANDEZ CASTRO ATTORNEY Patented Sept. 28, 1937 warren stares assists PATENT @ii lQE.

AIR BRAKE SYSTEM Lizandro Fernandez Castro, Oakland, Calif. Application October 28, 1935, Serial No. 47,062

4 Claims.

This invention relates to improvements in air brake systems and more particularly to balanced control valves therefor. I

Valves of this type provide the accurate micrometric control of the brakes so necessary in modern high-speed heavy-duty trucks and trail ers. The fluid pressure in the system is automatically maintained by the valve at the exact differential corresponding to the particular position at which the control handle has been manually set. Heretofore valves of this type required extreme high precision manufacture and consequent expense which prevented their coming into general use. These prior valves were, moreover, subject to undue wear and unsatisfactory operation in the presence of abrasive dust inevitable in the operative conditions of the usual truck.

An object of the present invention is to provide a balanced control valve requiring but little precision in its production and capable of being manufactured at low cost without sacrificing accuracy in its operation.

Another object is to render the valve permanently reliable in operation and proof against deterioration under adverse working conditions.

Another object is to obviate the necessity for employing skilled mechanics to service the valve.

Other objects and advantages appear as the description progresses.

In this specification and the accompanying drawing the invention is disclosed in its preferred form. It is, however, to be understood thatit is not limited to this form because it may be embodied in other forms within the purview of the claims following the description.

In the one sheet of drawings:

Fig. 1 is a side elevation diagrammatically illustrating an installation of a valve constructed in accordance with this invention.

Fig. 2 is an enlarged vertical section of the same.

Fig. 3 is a fragmentary elevation of the valve cam taken at right angles to Fig. 2.

In detail, the construction illustrated in the drawing, referring more particularly to Figs. 1 and 2; comprises thevalve body I having the central tubular portion 2. The outlet 3 communicates with the interior of the tube 2 and is connected by the pipe 4 to a source of subatmospheric pressure, such as the motor intake manifold'. The outlet 6 communicates with the space within the body I around the tubular por tion 2 and is connected to the brake power chamber I by the pipe 8. The power chamber 1 is conventional in design and mounting and may 01. soc-4,4) v

be modified to meet conditions as usual within the skill of the art.

The tubular portion 2 has the annular valve seat 9 around its lower end. The valve diaphragm H3 is engageable with the seat 9 and has its margins confined between theabutting flanges of the body I and the cover H. The screws l2 secure the cover I l to thebody l. The diaphragm it! has its central portion clamped between the disks l3 and Mby the rivet Hi. The disk l3 provides a firm backing for the portion of the diaphragm engaging the seat 9 while the disk I4 is of slightly less diameterto clear the annular seat 9. The disks l3 and iii serve to move the diaphragm ill relative to the seat 9 in the operation of the valve.

The cover H has the opening to admit atmospheric pressure maintains the valve diaphragm I5 therethrough which normally lil seated against the subatmospheric pressure on the opposite side thereof. The spring ll expanding between the cover II and the disk [3 provides additional pressure to maintain the diaphragm l0 normally seated.

The flexible diaphragm it is interposed between the flanges of the body l and the housing l9 which are secured together by the screws 20. The hollow plunger 2|, has the edges of the open central portion of the diaphragm secure-d thereto by the clamping ring 22 and the rivets 23. The ports 24 through the lower portion of the hollow plunger 2| permit flow of air from the housing I9 into the body I past the diaphragm l8.

Atmospheric pressure is admitted into the housing l9 through the openings 25. Deleterious dust and dirt particles arefiltered from the incoming air by the fibrous material 26 in the space around the neck 21. The fibrous material 26 is maintained in place by the perforated ring 28.

The piston 29, fixed on the plunger 2|, is slidable in the upper end of the tubular portion 2 of the body I and is a relatively loose fit therein. The piston 2| is reduced in diameter at its lower end and has the leather packing cup 30 fixed thereonby the washer 3i and the threaded stud 32. The pressure differential between the interior and the exterior of the tube 2 expands the skirt of the packing cup and prevents air leakage past the piston 29. This obviates high precision fitting of the piston 29 into the tube 2.

The spring 33 expanding between the washer St on the piston 28 and the disk M on the valve diaphragm l0 transmits the movement of the piston to the diaphragm to operate the valve as later described.

The tension of the spring I] is adjustable with respect to that of the spring 33 by means of the set screw H.

The sleeve 34 is rotatably mounted in the neck 21 in the housing l9 and extends upwardly therefrom and has the projecting serrated portion 35. The control handle 36 engages the serrations 35 and is manually operable to rotate the sleeve 34. The cap screw 3'! is threaded in the sleeve 34 to secure the handle 36 thereon. The sleeve 34 has the annular shoulder 38 opposing the thrust of the cap screw 37. This provides the necessary friction to maintain the handle 36 and the sleeve 34 in the position to which they have been manually moved. This friction may be varied by adjustment of the cap screw 31. The lock washer 39 retains the cap screw 31 in adjusted position.

The ball 46 occupies a slot in the handle 33 and is urged outward by the spring 4| and forms a yielding frictional stop engaging in notches such as 42 on the housing i 3. This serves as an audible and tactual indicator to the operator of the extent of the manual movement of the control handle.

The stem 43 is slidably mounted in the sleeve 34 and is reduced in diameter and threaded at its lower end. The valve disk 44 of soft material is backed up by the washer 45 and secured on the reduced end of the stem 43 by the guide 46. The hollow plunger 2| has the annular valve seat 47! which is adapted to be engaged by the valve disk 44 to close communication between the housing It and the body 5. The spring 48 encircles the stem 43 and expands between a ledge in the sleeve 34 and the collar 49 riveted on the end of the stem.

" This urges the stem 43 upward and normally maintains the valve disk 44 unseated.

The pin 54 extends laterally through the stem 34 and has its ends confined in the vertical grooves 5| in the neck 21 to prevent rotary movement of the stem. The lower end of the sleeve 34 has the annular end cam 52 thereon, see also Fig. 3, which engages the pin 50. Rotation of the sleeve 34 by operation of the control handle drives the pin 59 downward and seats the valve disk 44.

The invention operates substantially as follows: Inthe inoperative position shown in Fig. 2 the valve diaphragm I it engages the seat 9 cutting off the power chamber outlet 6 from the subatmospheric pressure outlet 3. The valve disk 44 is unseated allowing atmosphere from the openings 25 in the housing I 9 to flow into the body I after having passed through the filter 26. The pipe I 8 conducts this atmospheric pressure to the brake power chamber l to maintain the brakes inactive.

To apply the brakes. the operator manually swings the handle 36 an extent corresponding to the degree of brake application desired. The cam 52 rotates against the pin and drives the stem 43 downward. The valve disk 44 engages the seat 41 and forces the plunger 2! and the piston 29 downward. The closing of the valve 44-41 cuts off the power chamber I from communication with. the atmosphere.

The downward movement of the piston 29 compresses the spring 33 providing the necessary force to unseat the valve diaphragm l0 against the tension of the spring I i and the atmospheric pressure on the other side thereof. Unseating the diaphragm 53 provides communication between the outlets 3 and 5. The reduced pressure in the intake manifold 5 then quickly evacuates the power chamber 1 down to a predetermined pressure depending upon the extent of the movement of the operating handle 36. The pressure differential thus created in the power chamber applies the brakes to the degree desired by the usual means (not shown).

The incidental evacuation of the interior of the body I around the tubular portion 2 produces an additional subatmospheric pressure on the portion of the diaphragm I6 surrounding the seat 9. The pressure differential is now exerted over the whole area of the diaphragm.

The pressure in the power chamber and the body I continues falling until it reaches a certain critical point depending upon the amount of compression of the spring 33 which is controlled by the operating handle 36. At this point, the fluid pressure differential on the diaphragm it plus the tension of the spring I? overbalances the pressure of the compressed spring The diaphragm is then forced back into engagement with the seat 9 cutting off the power chamber i from communication with the intake manifold 5. This stabilizes the pressure in the power chamber and maintains the brakes applied to the degree desired.

When the diaphragm Ill once engages the seat 9, the intake manifold exhausts the tubular portion 2 to a lower pressure than the remainder of the interior of the body. This tends to engage the diaphragm l0 firmly against the seat 9 preventing air leakage therepast.

A pressure differential is also exerted on the diaphragm I8 by the evacuation of the body I. At the critical pressure above referred to, the force of the pressure differential is almost equal to the reaction of the compressed spring 33. Should the power chamber 1 be evacuated to below the critical pressure, the pressure differential on the diaphragm it will overbalance the force of the spring 33 and move the seat 47 from engagement with the valve 45. Atmosphere admitted into the body 5 past the unseated valve will correct the pressure in the power chamber I. When the critical pressure is again restored the spring 33 will automatically move the seat 4? into engagement with the valve 45 cutting off the supply of atmospheric air to the power chamber. The light cont-act of the seat 4'! against the soft valve 45 due to the balancing of opposed forces at the critical pressure protects the valve against excessive wear and prolongs its life.

Should it be desired to apply the brakes more firmly, the control handle 35 is operated accordingly. The cam 52 drives the stem 43 and valve disk 44 downward thus forcing the plunger 2| and the piston 29 down still farther. This further compresses the spring 33 thereby overcoming the previously counterbalanced forces acting on the diaphragm It].

The diaphragm E4 is thus again unseated and the evacuation of the power chamber continued to apply the brakes an additional extent. The pressure differential on the diaphragm it increases until another critical pressure is reached when the forces acting on the diaphragm again overbalance the pressure of the compressed spring 33. The diaphragm is then seated again stabilizing the pressure in the power chamber 1.

The brakes may be partially released by moving the control handle 35 toward the original inoperative position. The reverse rotation of the cam 52 enables the spring 48 to raise the stem 43 to unseat the valve disk 44. Air at atmospheric pressure then flows through the housing 19 past the unseated valve disk 44 to the power chamber 1. The pressure in the power chamber then rises and progressively releases the brakes.

The unseating of the valve disk 44 leaves the plunger 21 free to travel upward under the tension of the compressed spring 33. When the pressure in the brake system reaches a critical point corresponding to the particular position of the control handle, the spring 33 engages the seat 41 against the valve disk 44. This cuts off the supply of atmospheric air to the power chamber l and stabilizes the pressure therein.

For complete release of the brakes, the control handle 36 is moved into its original inoperative position. The spring 48 raises the valve disk 44 to the level shown in Fig. 2. The diaphragm I8 is of restricted area. This prevents the spring 33 raising the plunger 2| sufliciently to bring the seat 41 into engagement with the valve 44. This produces complete restoration of atmospheric pressure in the power chamber 1 thus fully releasing the brakes.

When the control handle 36 is swung into the extreme operative position, the cam 52 depresses the piston 29 until the stud 32 thereon engages the rivet I5 on the valve diaphragm II]. This holds the diaphragm unseated until the control handle is moved out of its extreme position. While the diaphragm is thus unseated, the power chamber 1 is evacuated to the minimal pressure of the intake manifold. This assures rapid maximum application of brakes when required in emergencies.

Having thus described this invention what is claimed and desired to be secured by Letters Patent is:

1. An air brake. system having an air pressure actuated element and a control including a body with an outlet communicating with said pressure actuated element; a pair of diaphragms in said body arranged on opposite sides of said outlet and having their outer surfaces exposed to atmospheric pressure; resilient means interposed between said diaphragms and adapted to resist contraction thereof; valve means interposed between said pressure actuated element and a source of subatmospheric pressure and adapted to be closed by the contraction of one of said diaphragms toward the other; a second valve interposed between said pressure actuated element and. the atmosphere and adapted to be opened by the contraction of the second diaphragm toward the. first; manual control means adapted to close said atmospheric valve and thereby to move said second diaphragm toward said first and to increase the tension of said resilient means.

2. An air brake system having an air pressure actuated element and a control including a body with an outlet communicating with said pressure actuated element; a diaphragm in said body arranged in juxtaposition to said outlet and exposed to atmospheric pressure on the opposite side thereof; valve means interposed between said pressure actuated element and a source of subatmospheric pressure; and adapted to be closed by the movement of said diaphragm toward said outlet; a second diaphragm in said body arranged on the opposite side of said outlet and having a central opening therethrough communicating with the atmosphere; an annular valve seat surrounding said opening; a valve adapted to cooperate with said seat and move said diaphragm; said valve being unseated by the movement of said second diaphragm toward said outlet; manual control means for regulating the position of said valve; and resilient means interposed between said diaphragm and arranged to resist their movements toward said outlet.

3. An air brake system having an air pressure actuated element and a control including a body with a central tubular portion and outlets from the exterior and the interior of said tubular portion communicating with said pressure actuated element and a source of subatmospheric pressure respectively; a valve seat at the end of said tubular portion; a valve diaphragm in said body adapted to cooperate with said seat and exposed to atmospheric pressure on its opposite side; a second diaphragm in said body arranged on the opposite side of said tubular portion and having a central opening communicating with the atmosphere; a hollow plunger in said opening having ports therethrough and a valve seat thereon; a

piston fixed to said plunger and closing the end of said tubular portion; resilient means interposed between said piston and said valve dia phragm; a valve adapted to cooperate with the seat on said plunger and to move said diaphragm; and control means for regulating the position of said valve.

4. An air brake. system having a pressure actuated element and a control including a body with a central tubular portion and outlets from the exterior and the interior of said tubular portion communicating with said pressure actuated element and a source of subatmospheric pressure respectively; a diaphragm in said body and arranged to control valve means at one end of said tubular portion; a second diaphragm arranged on the opposite side of said outlet and having a central opening therethrough communicating with the atmosphere; an annular valve seat surround ing said opening; a valve adapted to cooperate with said seat and move said diaphragm; control means for regulating the position of said valve; a piston fixed on said second diaphragm and slid able in the end of said tubular portion; a packing cup on said piston expanding against the sides of said tubular portion to prevent air leakage; and resilient means interposed between said piston and the first diaphragm.

LIZANDRO FERNANDEZ CASTRO. 

